Nickel plating

ABSTRACT

THE NOVEL PROCESS OF THIS INVENTION FOR ELECTROPLATING A SEMI-BRIGHT SUFLUR-FREE, NICKEL PLATE ONTO A BASIS METAL COMPRISING PASSING FROM AN ANODE TO A BASIS METAL CATHODE THROUGH AN AQUEOUS ACIDIC NICKEL PLATING SOLUTION CONTAINING AT LEAST ONE NICKEL COMPOUND PROVIDING NICKEL IONS FOR ELECTROPLATING OF NICKEL, AND INCLUDING AS COOPERATING SEMI-BRIGHT ADDITIVES: (A) THE ALIPHATIC ACETYLENIC COMPOUND 3-HEXYNE-2,5-DIOL, AND (B) A COMPOUND CONTAINING AN OXYAMEGASULFOHYDROCARBON-DI-YL COUMARIN ANION WHEREIN THE HYDROCARBON-DI-YL MOIETY CONTAINS AT LEAST TWO CARBON ATOMS AND WHEREIN THE OXYOMEGASULFOHYDROCARBON-DI-YL GROUP IS SUBSTITUTED ON THE CARBOCYLIC NUCLEUS OF THE COUMARIN GROUP.

United States Patent 3,677,913 NICKEL PLATING Frank Passal, Detroit,Mich., assignor to M & '1 Chemicals, Inc., Greenwich, Conn. No Drawing.Filed Apr. 1, 1971, Ser. No. 130,479 Int. Cl. C23b 5/08, 5/46 US. Cl.204-49 12 Claims ABSTRACT OF THE DISCLOSURE The novel process of thisinvention for electroplating a semi-bright sulfur-free, nickel plateonto a basis metal comprising passing current from an anode to a basismetal cathode through an aqueous acidic nickel plating solutioncontaining at least one nickel compound providing nickel ions forelectroplating of nickel, and including as cooperating semi-brightadditives: (a) the aliphatic acetylenic compound 3-hexyne-2,5-diol, and(b) a compound containing an oxyomegasulfohydrocarbon-di-yl coumarinanion wherein the hydrocarbon di yl moiety contains at least two carbonatoms and wherein the oxyomegasulfohydrocarbon-di-yl group issubstituted on the carbocyclic nucleus of the coumarin group.

This invention relates to the electroplating of a semibright nickelcharacterized by its fine grain, uniformity, ductility, freedom fromsulfur, and by its high leveling ability.

When it is desired to produce a nickel surface possessing maximumbrightness and luster and/or when the surface of the basis metal maypossess numerous scratches or other minor imperfections, it is common toelectroplate onto the surface a first layer of nickel particularlycharacterized by its leveling ability. This deposit is called asemi-bright nickel deposit because it does not posses the extremely highbrilliance and luster commonly attained by a bright-nickel deposit.There may commonly be deposited onto this first semi-bright nickel layera second bright nickel layer. The semi-bright nickel layer may forcertain applications be polished and buffed prior to deposition of thebright nickel layer. The resulting duplex-nickel system is characterizedby high degree of brilliance and by superior resistance to corrosion,even when the bright nickel deposit is relatively thin.

The first or semi-bright layer of nickel has heretofore commonly beendeposited from various nickel-plating baths, including for example Wattsbaths, sulfamate baths, chloride-free baths, etc. which contain anadditive or a combination of additives. One of such additives commonlyused in prior art semi-bright nickel plating baths has been coumarin.Although it may be possible to produce a semi-bright nickel deposit byprior art methods, there are numerous defects which render theseprocesses less than fully satisfactory. Semi-bright nickel depositsformed from some plating baths of the prior art also may sufier frominadequate leveling, high tensile stress, and non-uniform grain size.

In an effort to correct these deficiencies of semi-bright nickel platingbaths, various combinations of additives have been used some of whichhave been coumarin derivatives having various groups attached to thearomatic or to the heterocyclic ring. These compounds, however, havebeen found not to be satisfactory in that they do not 3,677,913 PatentedJuly 18, 1972 permit attainment of an improved semi-bright nickel plate,but rather they have suffered from defects such as very low solubility,difficulty of synthesis, and tendency to readily decompose duringelectrolysis to give undesirable products, typically resinous orpolymeric materials which result in inferior deposits, unsatisfactorydegrees of leveling and narrow ranges of leveling current density.

It is an object of this invention to provide a combination of additivesthat increase the luster, leveling, and the width of the levelingcurrent density range to increase the uniformity of deposits and grainsize and at the same time maintaining ductility and without creatinginternal stresses in the electroplating of semi-bright nickel. Otherobjects will be apparent to those skilled in the art on inspection ofthe following description.

The novel process of this invention for electroplating a semi-bright,sulfur-free, nickel plate onto a basis metal comprises passing currentfrom an anode to a basis metal cathode through an aqueous acidic nickelplating solution containing: at least one nickel compound providingnickel ions for electroplating of nickel and as cooperating semibrightadditives: (a) the aliphatic acetylenic compound 3-hexyne-2,5-diol and(b) a compound containing an oxyomegasulfohydrocarbon-di-yl coumarinanion wherein the hydrocarbon-di-yl moiety contains at least two carbonatoms and the oxyomegasulfohydrocarbon-di-yl group is substituted on thecarbocyclic nucleus of the coumarin group.

Practice of this invention results in a high degree of leveling and ahigh width of current density range to give optimum results in theplating of ferrous basis materials and rigid articles such as automobilebumpers. The novel combination of cooperating additives of thisinvention also eliminates the problem of maintaining low current densitydeposits sufiiciently lustrous and fine grained to provide sufiicientbuild-up of brightness in the low current density areas. All nickelplating bath in a commercial operation accumulate metallic (zinc,copper, etc.) and organic impurities (which may include decompositionproducts of the coumarin derivatives). The cooperating additives of theinvention reduce and minimize deleterious effects of such impurities.For example, if some of the organic impurities tend to givecoarser-grained, duller low current density deposits, the cooperatingadditives tend to counter-act these effects.

The basis metal onto which the semi-bright deposits of this bath may beapplied may include basis metals which are characterized by a low degreeof luster or brightness or which possess a degree of surface roughnesswhich would fail to permit attainment of a satisfactory quality of finalfinish and appearance if they were directly plated with a bright nickelplate. Typically the basis metals may include ferrous metals such assteel; copper, including its alloys such as brass, bronze, etc.; zinc,particularly in the form of die castings which may bear a plate ofcopper, etc.

The novel baths of this invention may typically include Watts-typebaths, sulfamate-type baths, fluoboratetype baths, chloride-freesulfalte baths, chloride-free sulfamate baths, etc.

A typical Watts bath which ma be used in practice of this invention mayinclude the following components in aqueous solution, all values beingin grams per liter (g./l.) except for the pH.

A typical sulfamate-type bath which may be used in practice of thisinvention may include the following components:

TABLE II Min- Max- Pre- Component imum irnum ferred Nickel sulfamate 330400 375 Nickel chloride 15 6O 45 Boric acid 35 55 45 pH electrometric 35 4. 0

A typical fluoborate-type bath which may be used in the practice of theinvention may include the following components:

TABLE I11 Min- Max- Pre- Compcnent inunn lmmn ferred Nickel fluoborate250 400 300 Nickel chloride 45 60 50 Boric acid 15 30 30 pHelectrometrlc 2 4 3. 0

A typical chloride-free sulfamate-type bath which may be used inpractice of this invention may include the following components:

TABLE IV Min- Max- Pre- Component imum imum fened Nickel sulfate- 300500 400 Boric acid 55 45 pH electrornetric 3 5 4. 0

A typical chloride-free sulfate-type bath which may be used in practiceof this invention may include the following components: I

TABLE V Min- Max- Pre- Component imnrn imum ierred Nickel sulfamate 300400 350 Boric acid 35 55 45 pH electrometric 3 5 4. 0

In the above bath compositions nickel sulfate is present as NiSO -7H Oand nickel chloride as NiCl -6H O; all other compounds are given astheir anhydrous form.

It will be apparent that the above baths may contain compounds inamounts falling outside the preferred minima and maxima set forth, butmost satisfactory and economical operation may normally be effected whenthe compounds are present in the baths in the amounts indicated. Apartciular advantage of the chloride-free baths of Tables 1V and V,supra, is that they may be used for high speed plating with insolubleanodes, such as lead, or with soluble anodes having low polarizationtendency, such as SD nickel, to avoid the possible evolution of toxicchlorine gas at the anode.

Only an amount of cooperating additive sufiicient to provide improvedplating characteristics for the nickel plating solution containing atleast one nickel compound providing nickel ions for electroplatingnickel is necessary. The amount of the first cooperating additive, thealiphatic acetylenic compound 3hexyne-2.5-diol, presem; in the nickelplating solution shown be from 0.1 gram per liter to 1.0 gram per liter,preferably from 0.2 gram per liter to 0.8 gram per liter. Theconcentration of the second cooperating additive, a compound containingthe oxyomegasulfohydroearbon-di-yl group present in the nickel platingsolution should be from 0.2 gram per liter to 1.0 gram per liter,preferably from 0.4 gram per liter to 0.8 gram per liter.

The second cooperating semi-bright additive employed in practice of thisinvention comprises compounds containing theoxyomegasulfohydrocarbon-di-yl coumarin anion wherein the hydrocarbonmoiety contains at least two carbon atoms. Theoxyomegasulfohydr'ocarbon-di-yl group is substituted on the carbocyclicring of the coumarin nucleus. The hydrocarbon-di-yl moiety may bearinert substituents. Typically such compounds include those wherein thecation M (see infra) may be a bath-compatible cation, i.e. a cationwhich is soluble in the electroplating bath and which does not interferewith attainment of the desired semi-bright plate. Typically, the cationM includes hydrogen and alkali metals including sodium, potassium,lithium, etc.; polyvalent metals such as nickel, cobalt, magnesium, etc.The omega carbon atom of these novel compounds is the carbon atomlinking the sulfo group to the remainder of the molecule. Most commonlythe omega position is the carbon atom most distant from the coumarinnucleus. However, when a hydrocarbon-diy1 group in the chain linking thecoumarin nucleus to the sulfo group contains carbon-containingsubstituents, the omega position as herein defined may not be the carbonatom most distant from the coumarin nucleus.

The cooperating acetylenie additive used in cooperation with thecoumarin derivatives, besides increasing the general deposit luster anduniformity and acting as a low current density coverage and lusterpromoter, also acts as an extender and markedly improves leveling.

The compounds containing the oxyomegasulfohydrocarbon-di-yl coumarinanion typically have the following formula:

HJII-O-SOa-R-OL, (I)

wherein a, b, c and d are each integers less than two, i.e. 0 and 1, thesum of a, b, c and at being greater than 0 and preferably 1 and whereinM is a cation as defined supra, R is a hydrocarbon-di-yl group whereinthe hydrocarbon moiety contains at least two carbon atoms, and X is aninert substituent. Typically inert substituents (i.e. substituents whichdo not cause unfavorable efiects to occur in electroplating bathsincluding the novel compounds of this invention), include hydrogen;halogen, e.g. chloro; alkyl, alkaryl, aralkyl, aryl, alkoxy, aryloxy,etc. As shown, the inert substituent when present is preferably on thearomatic ring of the coumarin nucleus.

In the above formula R may be a divalent hydrocarbon group having atleast two carbon atoms. Typically R may be arylene such as o-phenylene,m-phenylene, pphenylene; aralkylene such as o-benzyl, m-benzyl orpbenzyl; alkarylene such as l-methyl-2,3-phenylene, 1-methyl-2,4-phenylene, l-methyl 2,5 phenylene, etc.; alkylene such asethane-1,2-di-yl, propane-1,2-di-yl, propane-1,3-di-yl,butane-1,4-di-yl, bntane-l,3di-yl, pentane- 1,5-di-yl, etc. These groupsmay bear inert substituents including hydrocarbon substituents. Thepreferred R group may contain at least three carbon atoms, and morepreferably 3-5 carbon atoms in a straight chain extending from thecarbon atom closest to the coumarin nucleus to the omega carbon atom,the omega position being as hereinbefore defined. Preferred R groups maycontain a linked 5 chain of methylene groups and the most preferred Rmay be propane-1,3-di-yl, CH CH CH In formulae containing a plurality ofR groups, the R groups may preferably be the same.

With respect to Formula I supra, it will be apparent that when a is 1, bis 1, c is 0, and d is the formula is:

M-OS OPE- 0 (II) and that when a is O, b is 1, c is l, and d is 0 theformula may be:

(III) and that when a is 0, b is l, c is 0, and d is 0 the formula maybe:

It will be apparent that the values of a, b, c, and d may beindependently varied between 0 and 1 to produce coumarin derivativesother than those specifically set forth.

It will also be apparent that when M is polyvalent, the valences thereofmay be satisfied by linkage to other oxyomegasulfohydrocarbon-di-ylgroups which may be on the same or on another coumarin nucleus.

The preferred compounds include those wherein theoxyomegasulfohydrocarbon-di-yl group is substituted on the 7-position ofthe coumarin and M is an alkali metal; also preferred are thosecompounds wherein R is a hydrocarbon-di-yl group having 3-5 carbon atomsand most preferably one wherein R is a polymethylene chain preferablyhaving 3 carbon atoms. Typical preferred specific compounds which may beused in practice of this invention include:

TABLE VI potassium 7-oxyomegasulfopropyl coumarin potassium6-chloro-7-oxyomegasulfopropyl coumarin sodium 7-oxyomegasulfopropylcoumarin sodium 6-chloro-7-oxyomegasulfopropyl coumarin disodium6,7-di(oxyomegasulfopropyl) coumarin disodium7,8-di(oxyomegasulfopropyl) coumarin nickel 6,7-di(oxyomegasulfopropyl)coumarin cobalt 7,8-di(oxyornegasulfopropyl) coumarin nickeldi(7,7'-oxyomegasulfopropyl) coumarin potassium 8-oxyomegasulfopropylcoumarin potassium 6-oxyomegasulfopropyl coumarin sodium-oxyomegasulfobutyl coumarin potassium 7-oxyomegasulfobutyl coumarinsodium 7-0xyomegasulfobenzyl coumarin (i.e., sodium 7-oxy-orthosulfobenzyl coumarin), viz:

The 'most preferred compounds may typically be the first four compoundsin Table IV. It will be apparent that other cations as hereinbeforenoted may replace those present in the specific compounds in Table VI.

The oxyornegasulfohydrocarbon-di-yl coumarin compounds of thisinvention, wherein the hydrocarbon-di-yl moiety contains at least 2carbon atoms and the oxyomegasulfohydrocanbon-di-yl is substituted onthe carbocyclic nucleus of the coumarin group, may be prepared by theprocess which comprises mixing in a solvent dispersion, a hydroxycoumarin wherein the hydroxy group is substituted on the carbocyclicnucleus of the coumarin group, a compound of the formula MOH wherein Mis a cation including those hereinbefore noted, and a hydrocarbonsultone wherein the hydrocarbon moiety contains at least 2 carbon atomsthereby forming a reaction mixture, and heating said reaction mixture.

The solvents used in this preparation may preferably be those in whichthe reactants are dispersible, i.e. suspendable or soluble and mostpreferably one in which the compound MOH is soluble. Such solvents maytypically include organic solvents such as alcohols, etc.

The sultones which may be employed to prepare the novel compounds ofthis invention may include those containing acarbon-oxygen-sulfur-carbon linkage in a ring, the hexavalent sulfuratom being further bonded to two additional oxygen atoms. The sultonewhich may preferably 'be used may contain 3-5 carbon atoms, thesesultones being characterized by generation of a minimum of foaming. Themost preferred sultone may be 1,3-propane sultone,

although sultone such as 1,4-butane sultone,

and 1,3-butane sultone,

also may produce highly useful additives. The longer chain alkanesultones or other sultones containing more than 5 carbon atoms, such astolyl sultone,

may also be used to produce additives within the scope of the invention.

Hydroxy-coumarins which may be used in preparing the novel compounds mayinclude the following hydroxy coumarins which carry one hydroxylsubstituent on the carbocyclic nucleus of coumarin, typically includingmonoand poly-hydroxy coumarins such as:

S-hydroxy coumarin 6-hydroxy coumarin 7-hydroxy coumarin 8-hydroxycoumarin 6,7-dihydroxy coumarin 7,8-dihydroxy coumarin6-chloro-7-hydroxy coumarin Preferred coumarins may include the7-hydroxy coumarins such as 7-hydroxy coumarin, per se.

These hydroxy coumarins may be readily available or may be prepared bythe reaction of the corresponding resorcinol with malic acid in thepresence of catalyst, e.g. concentrated sulfuric acid, e.g. to prepare6-chlor0 7-hydroxy coumarin, malic acid may be reacted with 4-chlororesorcinol. Besides concentrated sulfuric acid other catalysts may beused such as the pyrophosphates of titanium and zirconium used singly orin combination.

The preferred compounds MOH which may be used in the process of thisinvention include alkali metal hydroxides such as sodium hydroxide,potassium hydroxide and lithium hydroxide.

In a preferred embodiment of the invention, 2.3-3.3 parts, say 2.8 partsof MOH, preferably potassium hydroxide, may be added to 3-4 moles, say3.1 moles of solvent, preferably methanol. 7541 parts, preferably 8.1parts of 5-, 6-, 7- or S-hydroxy coumarin, preferably 7- hydroxycoumarin, may then be added together with 4.9- 7.3 parts, say 6.7 partsof hydrocarbon sultone, preferably 1,3-propane sultone. Preferably themolar ratio of MOH to hydrocarbon sultone may be about 1 to 1.. Thereaction mixture may then preferably be heated typically to refluxtemperature for 1-4 hours, say 2 hours. All parts referred to above areparts by weight.

At the conclusion of the reaction time the reaction vessel may be cooledand the desired product may precipitate. The product may be separated,washed with a solvent in which the product is sparingly soluble, such asmethanol, and dried. Typically the pure yield may be at least about 60%by weight based on the coumarin starting material, although crude yieldmay also be used as semi-bright additives to electroplating bathswithout deleterious results. Alternatively, the solvent, such asmethanol, may be removed by heating under reduced pressure and theresidual product dissolved in water to a convenient concentration andused as the additive stock solution to essentially obtain a quantitativeyield of the active ingredient.

If it be desired to convert the alkali metal salt of theoxyomegasulfohydrocarbon-di-yl coumarin to other salts, the alkali metalsalt of the oxyomegasulfohydrocarbondi-yl coumarin compound maypreferably be reacted with a cationic exchange resin such as a sulfonicacid cationic exchange resin on the hydrogen cycle. The free sulfonicacid in the eluate may then be reacted with the oxide, hydroxide,carbonate, etc., of the metal desired, e.g. nickel or cobalt toneutrality to form the desired metal salt of the free sulfonic acid. Anyexcess of the oxide, hydroxide, carbonate, etc., may be removed byfiltration.

The semi-bright oxyomegasulfohydrocarbon-di-yl coumarin moiety whereinthe hydrocarbon-di-yl moiety contains at least two carbon atoms andwherein the oxyomegasulfohydrocarbon-di-yl group is substituted on thecarbocycl-ic nucleus of the coumarin group may preferably be used innickel plating baths such as those of Table I-V. in amounts of at least0.2 g./l. of plating bath. Lower concentrations may give appreciablegrain refinement but the deposits may be less glossy. When theconcentration of the oxyomegasulfohydrocarbon-di-yl compound or groupexceeds 3 g./l. of plating bath, the results obtained generally do notprovide additional advantages over the lower ranges. The preferredconcentration ranges from about 0.51 g./l. of additive in the platingbath.

The presence of the cooperating additive 3-hexyneand low foaming anionicwetting agents such as sodium dialkyl sulfosuccinates may be used withair agitation. Although these wetting agents may commonly containsulfur, it has unexpectedly been found that no increase in the sulfurcontent of the nickel deposits may be observed when these wetting agentsare used with the semibright cooperating additives of the invention. Theuse of formaldehyde as an auxiliary additive is usually not necessarybut it may be used if desired and is compatible with the othercooperating additives.

It is a particular feature of this invention that medium or veryhigh-speed electroplating of semi-bright nickel may be eifected by theprocess comprising passing current from a substantially non-polarizinganode to a basis metal cathode through an aqueous nickel platingsolution including at least one nickel compound capable of providingnickel ions for electroplating nickel and as a first cooperatingsemi-bright additive 3-hexyne-2,5-diol and as a second semi-brightadditive a compound containing oxyomegasulfohydrocarbon-di-yl coumarinanion wherein the hydrocarbon moiety contains at least two carbon atomsand the oxyomegasulfohydrocarbon-di-yl group is substituted on thecarbocyclic nucleus of the coumarin group, maintaining the cathodecurrent density during said plating at a level of at least 10 amperesper square decimeter (ASD), and maintaining a high relative velocitybetween said nickel plating solution and said basis metal cathodethereby obtaining a glossy, leveled, semi-bright high-speed nickel platewith good low current density coverage and good ductility.

Semi-bright nickel plating in accordance with this invention may also becarried out under lower speed conditions by immersing a basis metalcathode into a nickel plating bath as hereinbefore disclosed. The anodemay be either a soluble anode, typically nickel metal, or an insolubleanode, typically lead.

If nickel is used as the anode, it is preferably SD type of nickel andplating may be carried out in chloride-containing baths for 30-60minutes, say 30 minutes at 40-60 C., say 50 C., with mechanical or airagitation.

The current density may typically be 2.5-5 a.s.d., preferably 5 a.s.d.

The novel process of this invention may permit attainment of a 12.5 to50 microns, says 25 microns of semi bright nickel plate characterized byits fine grain, high ductility, high gloss, uniform appearance, highleveling, and high covering power. The plate is also characterized byits essentially sulfur-free character.

The following examples illustrate the beneficial efiects of thecooperating additives comprising the aliphatic acetylenic compound3-hexyne-2,5-diol and compounds containing anomegasulfohydrocarbon-di-yl coumarin anion.

EXAMPLE 1 Nickel sulfate 300 g./1.

Nickel chloride 60 g./l. Boric acid 45 g./l. pH

4.0 electrometric.

To the above bath there was added the equivalent of 0.4 g./l. ofpotassium oxyomegasulfopropyl coumarin plus 0.1 g./l. formaldehyde plus0.25 g./l. sodium d-nhexyl sulfosuccinate and a Hull Cell test was rununder the following conditions:

Solution volume 267 ml.

Agitation n Magnetic stirring. Anode Electrolytic nickel. CathodePolished brass panel on which there was inscribed a single 1.25 cm. widehorizontal band of 4/0 grit emery scratches about 2.54 cm. from bottomedge of panel.

Temperature 50 C. Current 2 amperes. Time minutes.

After plating, the panel was water-rinsed, dried and examined. The highcurrent density end from about 7 to 12 a.s.d. showed a slightly milkywell-leveled deposit. From about 1 to 7 a.s.d. the deposit had only fairleveling and the luster was also only fair with some tendency toward ayellowish smeary haze. Below about one a.s.d. the deposit was lustrous.The deposit ductility was excellent.

EXAMPLE 2 EXAMPLE 3 Using the bath composition of Example 2 a 4-literlife test was run using the following conditions:

Plating cell-5 liter rectangular cross-section (13 cm. x 15 cm.) made ofPyrex.

Solution volume-4 liters to give a solution depth, in

absence of anode, of about 20.5 cm.

Temperature-45 C. (maintained by immersing cell in a thermostaticallycontrolled water bath).

Agitation--filtered air through a glass and polyethylene s ider.

An desingle bagged titanium basket containing SD nickel squares.

Cathode-brass strip (2.54 cm. x 20.3 cm. X 0.071 cm.) buffed andpolished on one side and immersed to a depth of about 17.8cm.-horizonta1 bend 2.54 cm. from bottom and the next 2.54 cm. bent togive an internal angle on the polished side of cathode of about45polished side facing anode at an approximate distance of 10.2 cm. andscribed vertically in center with a 1 cm. wide band of a single pass of2/0 grit emery paper scratches.

Cell current5.0 amperes.

Time-solution electrolyzed about 7 hours per dayoccasional cathodesplated for 30 minutes to evaluate deposit leveling, uniformity,ductility, luster (overall and in low current density recessed area).

Filtrationbatch, about every 200 ampere hours of total electrolysis.

Additions-the pH was periodically adjusted when necessary with dilutesulfuric acid to within a range of 3.8 to 4.2 electrometric; periodicadditions of the coumarin derivatives and 3-hexyne-2,5-diol were made tomaintain deposit luster, ductility and leveling.

10 Electrolysis was continued for a total of about 400 ampere hoursduring which time the following amounts of additives were consumed:

Grams Potassium oxyomegasulfopropyl coumarin 13.6 3-hexyne-2,5-diol 13.2

The life test started excellently and highly ductile, very uniformlyglossy, well-leveled deposits were obtained having practically zerointernal stress (as observed by lack of any tendency for the originallyperpendicularly positioned cathode to bend toward the anode). During thecourse of the life test the quality of the deposits was easilymaintained. The most remarkable and striking observation was that not asingle deposit plated showed any dullness, dull bands, or low currentdensity dullness, all of which are normally obtained with the coumarinderivative and formaldehyde as the cooperating additives unless carefuland periodic additions of the latter two additives are made veryfrequently. In other words, the 3- hexyne-2,5-diol permitted moreconsistent operational characteristics, i.e. it provided a basic grainrefinement and luster development which made possible wider fluctuationsin the coumarin derivative content without sacrificing the quality ofdeposit.

At the end of 400 ampere hours of operation, corresponding to acommercial operation of 50 days, assuming the use of 1 ampere per 4liters per 8 hour day, there was no indication of having reached a levelof additive degradation product accumulation which would necessitate apurification treatment. In addition, at the end of 400 ampere hours ofoperation the low current density recesses were lustrous and the depositlevelling, ductility and uniformity were excellent.

Although this invention has been illustrated by reference to specificexamples, numerous changes and modifications thereof which clearly fallwithin the scope of the invention will be apparent to those skilled inthe art.

I claim:

1. A process of electroplating a semi-bright sulfurfree, nickel plateonto a basis metal which comprises passing current from an anode to abasis metal cathode through an aqueous acidic nickel plating solutioncontaining at least one nickel compound providing nickel ions forelectroplating nickel; and, in an amount suflicient to provide improvedplating characteristics, as a first cooperating semi-bright additive thealiphatic acetylenic compound 3-hexyne-2,5-diol and as a secondsemi-bright additive a compound containing anomegasulfohydrocarbon-di-yl coumarin anion wherein the hydrocarbon-di-ylmoiety contains at least two carbon atoms and wherein theoxyomegasulfohydrocarbon-di-yl groups are substituted on the carbocyclicnucleus of the coumarin group.

2. The process of claim 1 wherein said second semibright additive isXid[MO-SO2R-O]d X1-e[Mo SOl R -O] X ,[M0S0aR-O] \O/0 X ,[MOS0gR0]..wherein X is an inert substituent, M is a cation, R is ahytdrocarbon-di-yl group containing at least two carbon atoms, and a, b,c, and d are each integers less than 2, the sum of a, b, c, and d beingat least 1.

3. The process of claim 1 wherein said second semibright additive is 1 1wherein M is a cation and X is an inert substituent.

4. The process of claim 1 wherein said first semi-bright additive ispresent to the extent of at least about 0.1 g./ I; of the solution andthe cooperating second semi-bright additive is present to the extent of0.14.0 g./1. of the solution.

5. A process of electroplating a semi-bright nickel deposit whichcomprises passing current from a substantially non-polarizing anode to abasis metal cathode through a chloride-free aqueous acidic nickelplating solution including at least one metal compound capable ofproviding nickel ion for electroplating nickel; and, in an amountsufiicient to provide improved plating characteristics, as a firstcooperating semibright additive the aliphatic acetylenic compound3-hexyne-2,S-diol andas a second semi-bright additive a compoundcontaining oXyomegasulfohydrocarbon-di-yl coumarin wherein thehydrocarbon moiety contains at least two carbon atoms and theoxyomegasulfohydrocarbon-di-yl group is substituted on the carbocyclicnucleus of the coumarin group; maintaining the cathode current densityduring said plating at at level of at least ten amperes per squaredecimeter, and maintaining a high relative velocity between saidchloridefree nickel plating solution and said basis metal cathodethereby obtaining a glossy leveled, semibright high speed nickel platecharacterized by good low current density coverage and good ductility.

6. A nickel plating solution comprising an acidic aqueous nickel platingsolution including: at least one nickel compound capable of providingnickel ions for electrodeposition of nickel on a basis metal cathode;and in an amount sufficient to provide improved plating characteristicsas a first cooperating semi-bright additive the aliphatic acetyleniccompound 3-hexyne-2,5-diol and as a second cooperating semi-brightadditive a compound containing an oxyomegasulfohydrocarbon-di-ylcoumarin ion wherein the hydrocarbon moiety contains at least two atomsand the oxyomegasulfohydrocarbon-di-yl group is substituted on thecarbocyclic nucleus of the coumarin group.

7. The nickel plating solution of claim 6 wherein the semi-brightadditive is 12 wherein X is an inert ,substituent, M is a cation, R is ahydrocarbon di-yl group containing atflea'st two carbon atoms, and a, b,c, and d are each integerslessthan 2, the sum of a, b, c, and ,dbeing atleast 1. V 8. The nickel platingsolution of claim '6 wherein 'saidsemi-bright additive'isf i wherein M is a cation and X is an inertsubstituent. 9. The nickel plating solution of claim 6 wherein saidsemi-bright additive is wherein M is a cation.

10; The nickel plating Solutibil of claim 5' wherein said semi-brightadditive is nearen-ces caea UNITED STATES PATENTS I p 3,367,854 2/ 1968Passal 204 49 3,556,959" 1/1971 1 Passal I. 204-49 GERALD L. KAPLAN;Primary Examiner

